Spinal stabilization surgical method

ABSTRACT

Spinal fusion implants are inserted into a disc space of disc material separating first and second vertebrae by forming bores between the vertebrae. A distraction spacer is temporarily put in place on one side of the vertebrae while a bore is being formed on an opposite side of the vertebrae.

This is a continuation, of application Ser. No. 08/015,863, filed Feb.10, 1993, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention pertains to a spinal stabilization surgical procedure.More particularly, this invention pertains to a method for implanting afusion spinal implant between two vertebrae.

2. Description of the Prior Art

Chronic back problems cause pain and disability for a large segment ofthe population. In many cases, the chronic back problems are attributedto relative movement between vertebrae in the spine.

Orthopaedic surgery includes procedures to stabilize vertebrae. Commonstabilization techniques include fusing the vertebrae together.

Fusion techniques include removing disc material which separates thevertebrae and impacting bone into the disc area. The impacted bone fuseswith the bone material of the vertebrae to thereby fuse the twovertebrae together.

As in any surgical technique, it is desirable in back surgery to providea procedure which permits rapid post-operative recovery. To this end andto increase the probability of a successful fusion, spinal implants havebeen developed. An example of such a spinal implant is shown in commonlyassigned and co-pending U.S. patent application Ser. No. 07/702,351filed May 15, 1991 (claiming priority to Jul. 6, 1989). That patentapplication teaches a threaded spinal implant which includes a hollowcylinder into which bone chips or bone slurry may be placed. Thecylinder has holes extending radially therethrough. The bone materialgrows through the holes to fuse with the bone material of the vertebrae.

A threaded spinal implant is also shown in U.S. Pat. No. 5,015,247,dated May 14, 1991. In addition to teaching a threaded spinal implant,U.S. Pat. No. 5,015,247 shows a method of implantation including certaintools to form a bore into which the implant is threaded.

A threaded fusion cage and a method of inserting such a cage is alsoshown in U.S. Pat. No. 4,961,740 to Ray et al. dated Oct. 9, 1990 aswell as U.S. Pat. No. 5,026,373 to Ray et al. dated Jun. 25, 1991. Thelatter patent teaches preparing a bore for the implant by drilling overa pilot rod. In addition to the above, spinal implants are shown in U.S.Pat. No. 4,875,915 to Brantigan dated Nov. 7, 1989, German Patent3505567A1 dated Jun. 5, 1986 to Vich, U.S. Pat. No. 4,834,757 toBrantigan dated May 30, 1989 and U.S. Pat. No. 4,507,269 to Bagby datedFeb. 27, 1985. The latter is not a threaded implant but uses a cage orbasket which is impacted into a bore formed between bone to be fused.

When performing back surgery (such as placing implants in a spine) it isdesirable that the surgical procedure be performed as quickly and asaccurately as possible. Accordingly it is an object of the presentinvention to provide a surgical procedure for placing an implant in aspine in a procedure which can be done quickly and accurately.

In addition to the foregoing, it is known to be desirable to place twoimplants between opposing vertebrae (although a single implant proceduremay be advisable in some circumstances). In a two implant procedure,bores are formed on opposite sides of the vertebrae to receive each ofthe implants. I have found that in such a procedure, the forming of thebores can cause misalignment of the vertebrae which is undesirable.Also, prior art techniques (e.g., drilling over a guide rod) can resultin a bore which does not cut equally into both vertebrae. Accordingly,it is a further object of the present invention to provide a surgicalimplant procedure which assures accurate alignment of the vertebraethroughout the procedure.

Furthermore, it is an object of the present invention to provide asurgical procedure that can be performed posteriorly, anteriorly or as alaparoscopic procedure.

SUMMARY OF THE INVENTION

A surgical method for implanting at least two spinal fusion implantsinto a disc space of a disc material which separates two vertebrae isdisclosed. The surgical method includes the steps of distracting oneside of the disc space with a spacer and forming an implant receivingbore in an opposite of the disc space. After implanting the implant intothe opposite side, the spacer is removed and a bore receiving implant isformed to receive a second implant.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation view of an implant for use with the method ofthe present invention;

FIG. 2 is the view of the implant of FIG. 1 with the implant rotated 90°about its axis;

FIG. 3 is a view taken along line 3-3 of FIG. 1;

FIG. 4 is a view taken along lines 4-4 of FIG. 3;

FIG. 5 is a view taken along lines 5-5 of FIG. 2;

FIG. 6 is a view taken along lines 6-6 of FIG. 3;

FIG. 7 is a cross-sectional side view of an end cap for use with theimplant of FIG. 1;

FIG. 8 is a plan view of the implant of FIG. 7;

FIG. 9 is a top plan view of an alignment guide assembly;

FIG. 10 is an end plan view of the guide assembly of FIG. 9;

FIG. 11 is a side elevation view of a drill tube guide removal handle;

FIG. 12 is a side elevation view of a drill tube guide;

FIG. 13 is a side elevation view of a drill tube planar according to thepresent invention;

FIG. 13A is a cross-sectional side view of the planar of FIG. 13;

FIG. 14 is a view taken along line 14-14 of FIG. 13;

FIG. 15 is a side elevation view of a starter vertebral reamer accordingto the present invention;

FIG. 16 is a proximal end view of the reamer of FIG. 15;

FIG. 17 is an enlarged side elevation view of a reamer head of thestarter reamer of FIG. 15;

FIG. 18 is a distal end elevation view of the reamer head of FIG. 17;

FIG. 19 is a side elevation view of an end cap inserter according to thepresent invention;

FIG. 20 is a distal end view of the inserter of FIG. 19;

FIG. 21 is a side elevation view of a starter alignment guide handle;

FIG. 22 is a side elevation view of a drill tube inserter cap;

FIG. 23 is a view taken along lines 23-23 of FIG. 22;

FIG. 24 is a distal end view of the inserter cap of FIG. 22;

FIG. 25 is a side elevation view of a distraction plug inserter;

FIG. 26 is a side elevation view of a slap hammer;

FIG. 27 is a distal end elevation view of the slap hammer of FIG. 26;

FIG. 28 is a side elevation view of a distraction plug for use with thepresent invention;

FIG. 29 is a side sectional view of a drill tube sleeve according to thepresent invention;

FIG. 29A is a side elevation view of a sheath for use with the presentinvention;

FIG. 29B is a distal end elevation view of the sheath of FIG. 29A;

FIG. 30 is a distal end elevation view of the drill tube sleeve of FIG.29;

FIG. 31 is a side elevation view of a drill tube for use with thepresent invention;

FIG. 32 is a view taken along line 32-32 of FIG. 31;

FIG. 33 is an enlarged side elevation view of a distal end of the drilltube of FIG. 31;

FIG. 34 is a side elevation view of a final vertebral reamer;

FIG. 35 is an elevation view of a proximal end of the final reamer ofFIG. 34;

FIG. 36 is an enlarged view of a reamer head of the reamer of FIG. 34;

FIG. 37 is an end elevation view of a distal end of the reamer head ofFIG. 36;

FIG. 38 is a side elevation view of a vertebral reamer guide pin;

FIG. 39 is a plan end view of the guide pin of FIG. 38;

FIG. 40 is a side elevation view of a starter tap;

FIG. 41 is a view taken along line 41-41 of FIG. 40;

FIG. 42 is an enlarged sectional view of thread cutting teeth of thetool of FIG. 40;

FIG. 43 is a side elevation view of an implant driver for use with thepresent invention;

FIG. 44 is an end view of a hub on a distal end of the tool in FIG. 43;

FIG. 45 is a view taken along line 45-45 of FIG. 43;

FIG. 45A is a side elevation view of a shaft of the tool of FIG. 43showing an attached collet;

FIG. 45B is a cross-sectional view of FIG. 45A taken along lines45B-45B;

FIG. 46 is a side elevation exploded view of a vertebral reamer handdriver;

FIG. 47 is an end elevation view of the tool of FIG. 46;

FIG. 48 is a side elevation view of two vertebrae separated by a disk;

FIG. 48A is a view taken along lines 48A-48A of FIG. 48;

FIGS. 49 and 49A are views similar to FIGS. 48, 48A showing insertion ofa starter alignment guide assembly;

FIGS. 50 and 50A are views similar to FIGS. 48 and 48A showing placementof a distraction plug by use of an inserter;

FIGS. 51 and 51A are views showing the distraction plug in place;

FIGS. 52, 52A are views similar to the preceding views showing placementof a vertebral reamer guide pin;

FIGS. 53, 53A are views similar to the foregoing views showing placementand use of a drill tube planar;

FIGS. 54, 54A are views similar to the foregoing views showing placementof a drill tube;

FIGS. 55, 55A are views similar to the foregoing showing placement of adrill tube sleeve;

FIGS. 56, 56A are views similar to the foregoing showing preboring of animplant bore;

FIGS. 57, 57A are views similar to the foregoing views showing apartially formed bore following the preboring of FIGS. 56, 56A;

FIGS. 58, 58A are views similar to the foregoing views showing finalboring of an implant bore;

FIGS. 59, 59A are views similar to the foregoing showing formation of acompleted bore after removal of the final boring tool of FIGS. 58, 58A;

FIGS. 60, 60A are views similar to the foregoing showing tapping of thebore formed in FIGS. 59, 59A;

FIGS. 61, 61A are views similar to the foregoing showing the tappedbore;

FIGS. 62, 62A are views similar to the foregoing showing placement of animplant within a threaded bore;

FIGS. 63, 63A are views showing completed placement of an implant withinthe bore;

FIG. 64 is a view showing placement of a drill tube using an end capinserter; and

FIG. 64A is a view showing use of a sheath on a drill tube.

DESCRIPTION OF THE PREFERRED EMBODIMENT

1. GENERALLY

Referring now to the several drawing figures in which identical elementsare numbered identically throughout, a description of the preferredembodiment will now be provided. For purposes of illustrating apreferred embodiment, a description of the surgical procedure will begiven with respect to an implant 10 such as that shown and described incommonly assigned and co-pending U.S. patent application Ser. No.07/702,351. It will be appreciated that the present surgical procedurecan apply to a wide variety of implants including threaded implants suchas those shown in the aforementioned U.S. Pat. Nos. 5,015,247 and4,961,740 as well as non-threaded implants such as shown in U.S. Pat.No. 4,507,269 or other implants. The term “implant” as used herein mayalso include bone implants (e.g., autograft, allograft or artificialbone).

The implant 10 (FIGS. 1-6) is a hollow cylinder 12 having male threads14 exposed on the exterior cylindrical surface of cylinder 12. Thecylinder includes a forward interior chamber 16 and a rear interiorchamber 17 separated by a reinforcing rib 19, a bone slurry or bonechips may be compacted into chambers 16,17 as will be described.

A first plurality of holes 18 extend radially through the cylinder walland communicate with the chambers 16,17. A second (and enlarged)plurality of holes 21 are disposed on diametrically opposed sides of theimplant 10.

A rear end 22 of the implant has a slot 24 which communicates with thechamber 17. The slot 24 allows the bone slurry or bone chips to beimpacted into the implant 10. A slot 25 is defined by rib 19. The slot25 is sized to receive the distal end of a tool (as will be more fullydescribed) to place the implant within a bore formed between opposingvertebrae.

An endcap 26 (FIGS. 7, 8) is provided to snap fit onto the rear end 12by means of snap tabs 27. In a preferred embodiment, the endcap 26 ispolyethylene or some other radiolucent material to permit post-operativex-ray inspection and determine the adequacy of the fusion after theimplant surgery has been performed.

2. TOOLS

A. Generally

In a preferred embodiment the technique of the present invention will beperformed with a prescribed kit of tools. For the purpose ofillustrating the preferred embodiment, the tools of the kit will now bedescribed. It will be appreciated that the method of the surgery can bepracticed using a wide variety of tools of different size and shapes.

Each of the tools of a kit necessary to perform the surgery as describedin this application will be separately described. The use of the toolswill become apparent with the description of the method of the inventionin Section IV.3 of this application. Unless otherwise specified, alltools are formed of stainless steel.

Since vertebrae size and disc space size vary from patient-to-patient(and since such sizes vary along the length of the spine of any givenpatient), several sizes of implants 10 are anticipated. Presently,implants 10 having minor outside diameters (D_(m)) of 3 mm, 5 mm, 7 mm,9 mm, 11 mm, 13 mm, 15 mm, 17 mm, 19 mm and 21 mm with lengths (L) of 10mm, 12 mm, 14 mm, 16 mm, 16 mm, 20 mm, 24 mm, 28 mm, 28 mm and 30 mm,respectively, are anticipated to accommodate various spine locations andsizes. The major outside diameters (D_(M)) Of the implants 10 are 2.5 mmlarger than the minor outside diameters D_(m).

Several of the tools to be described (e.g., reaming tool 126) are sizedfor particular sizes of implants. Namely, the reaming tool 121 must forma bore sized to receive the implant. Since ten sizes of implants areanticipated, ten sizes of boring tools 126 are anticipated as willbecome apparent to one of ordinary skill in the art.

B. STARTER ALIGNMENT GUIDE HANDLE

The kit of the present invention includes a starter alignment guidehandle 28 (see FIG. 21). The handle includes a distal end 30 having animpact flange 31 and an axially extending threaded stud 32. A proximalend 34 of the handle is knurled to permit a surgeon to firmly grip thehandle 28.

C. STARTER ALIGNMENT GUIDE ASSEMBLY

The starter alignment guide assembly 36 (FIGS. 9 and 10) includes a mainbody 40 having a threaded bore 42 sized to receive the threaded end 32of handle 28. Extending from the body 40 are parallel pins 44, 46. Thepins are spaced apart by a distance D₁ as will be more fully described.The pins 44, 46 have stop surface 45, 47.

As mentioned, since human anatomy varies significantly from one patientto another (and since the sizing of vertebrae varies depending on thelocation within the spine), it is anticipated that the kit will requirevarious sizes of tools. With respect to starter alignment guide assembly36, it is anticipated that at least ten tools will be provided havingpin spacings D₁ selected to identify a desired spacing of two implantseach of diameters of 3, 5, 7, 9, 11, 13, 15 17, 19, and 21 mm,respectively. However, such a kit will only require one guide handle 28which can be inserted and attached to each of the starter alignmentguide assemblies 36.

The main body 40 is nylon to be X-ray transparent. Also, the body 40 hascurved edges 49 with a radius of curvature to match a radius of acorresponding drill tube 92. For example, for placing two 13 mm (D_(m))implants 10, a drill tube 92 with an inside diameter of 16.0 mm (for aD_(M) of 15.5) is required (the 0.5 mm difference providing clearance).The edges 49 match the contour of the drill tube 92 and are spaced apartequal to a spacing of the drill tube when operating on either the rightor left side. As a result, the back surface 43 of main body 40 may beplaced against the spine to outline an area which must be cleared forthe procedure. This aids the surgeon in determining the properlaminectomy size or required amount of vessel retraction.

D. DISTRACTION PLUG INSERTER

A distraction plug inserter 48 (FIG. 25) is provided and includes ashaft 50 and a handle end 51 which is knurled to provide a secure grip.A distal end 53 has a threaded shaft 52 extending axially therefrom. End51 has a larger diameter than shaft 50 to provide a surface 49 againstwhich slap hammer 192 (FIG. 26) may strike as will become apparent.

E. DISTRACTION PLUG

A distraction plug 54 (FIG. 28) is provided having a generallycylindrical body 56 with a tapered forward end 58. The rear end has areduced diameter portion 55 terminating at a flange 57 having a diameterthe same as the body 56. A threaded bore 62 is formed through the rearend to receive the threaded shaft 52 of the distraction plug inserter48. The body 56 is knurled to prevent undesired axial movement of theplug 54 after it is inserted.

As will be more fully described, the distraction plug 54 is used toinitially distract opposing vertebrae. The amount of desired distractionwill vary from patient to patient and from spine location to spinelocation. Accordingly, it is anticipated that distraction plugs havingdiameters D₂ ranging from 3 to 14 mm (by one millimeter increments)shall be included within the kit. Each of the distraction plugs fits onthe inserter 48 such that only one inserter 48 is required for the kit.

F. VERTICAL REAMER GUIDE PIN

A vertebral reamer guide pin 64 (FIGS. 38 and 39) is provided includinga generally cylindrical body 66 having a tapered forward end 68 and areduced diameter threaded rear end 70. The tapered forward end 68 hasthree flats 69 that grind away disc material when the pin 64 is securedto a starter reamer 112 (FIG. 15) as will be described.

As with the distraction plug 54, a wide variety of sizes of guide pins64 are anticipated to be required in the kit having diameters D₃ rangingfrom 3 through 14 mm (increasing by one millimeter increments). Forreasons that will become apparent, it is desired that all of the guidepins 64 have a threaded stud 70 of identical size.

G. DRILL TUBE GUIDE

A drill tube guide 72 (FIG. 12) is provided including a cylindricalshaft 74 and a distal end 76. The distal end 76 has a predeterminedmaximum outside diameter D₄. Provided on the axial face 78 of distal endis a bore 80 which is threaded and sized to receive stud 70 of the guidepin 64. A proximal end 82 (of diameter D₄) of the drill tube guide has athreaded bore 81 for purposes that will be described. End 82 terminatesat a flat axial face 83.

In application, various sizes of implants 10 will be required dependingon the anatomical sizing of the vertebrae to be fused. It is anticipatedthat implants 10 of ten different major outside diameters D_(M) will berequired to accommodate a wide variety of applications. Accordingly, thekit of the present invention will include ten drill tube guides havingoutside diameters D₄ to finally prepare bores to receive the three sizesof implants as will be described. The outside diameters D₄ are equal toD_(M) for each matching pair of implant 10 and drill tube guide 72.

H. DRILL TUBE PLANAR

In some applications, it may be desirable to plane a surface of avertebrae. For example, tissue may cover the surface of the vertebrae tobe bored. The various tools of the present invention should abutvertebrae bone to insure that an implant 10 is inserted to a properdepth. A drill tube planar 84 removes the tissue and provides a flatsurface on the vertebrae bone against which to place tools.

The drill tube planar 84 (FIGS. 13 and 14) includes a hollow tube 86having an inside diameter D₅. The distal end 88 of the drill tube planar84 includes a toothed rasp surface 85 to rasp away bone material as thedistal end 88 is placed against bone and the planar 84 is rotated aboutits axis. The proximal end 90 of the planar 84 includes a knurled handleto permit a surgeon to securely grasp the planar during the planingoperation.

As will be more fully described, in the anticipated method of thepresent invention, the planar 84 will slip over the drill tube guide 72with the diameter D₄ selected in close tolerance to D₅ (i.e., D₅ is 0.5mm larger than D₄). As a result, ten planars 84 are required to fit onthe ten sizes of drill tube guides 72.

The planar 84 includes an internal stop 87 positioned to oppose surface83 of guide 72 when the planar 84 is placed over guide 72. A clean outhole 89 is provided to clean out planar 84.

I. DRILL TUBE

A drill tube 92 (FIGS. 31, 32, and 33) is provided in the form of ahollow cylindrical tube 94. The distal end 96 of the tube 94 is providedaxially projecting teeth 98. The proximal end 99 of the tube 94 isflared outwardly for purposes that will become apparent. As will beapparent, ten sizes of tube 92 are required with inside diameters D₆ toslip in close tolerance over ten sizes of drill tube guide 72 (i.e., D₆is 0.5 mm larger than D₄).

The teeth 98 each have a length, T_(L), of preferably 3 mm. The valleys97 are flat to provide stop surfaces to hit bone as teeth 98 are forcedinto vertebrae. This helps prevent the drill tube 92 from being forcedtoo far into bone.

J. DRILL TUBE INSERTER CAP

As will be more fully described, the drill tube 92 is secured tovertebrae by forcing the teeth 98 into the vertebrae bone material. Thisis done by impacting the proximal end 99 of the drill tube 92. Aninserter cap 100 (FIGS. 22, 23 and 24) is provided in the form of asolid cylinder having an axial bore 102 with an inside diameter D₉terminating at a flat annular face 101. Diameter D₉ is slightly largerthan outside diameter D₄ of drill tube guide 72 (FIG. 12) so that cap100 can slip over end 82 of guide 72 with a stop surface 103 opposingend 83 and with surface 101 opposing flared end 99 of drill tube 92. Thecap 100 has an opposite flat end 104 against which a surgeon may impact.This impacts the drill tube 92 to force the teeth 98 into the bone of avertebrae.

K. DRILL TUBE SLEEVE

A drill tube sleeve 105 (FIGS. 29 and 30) is provided in the form of ahollow tube having a flat distal end and an outwardly flared proximalend 110. Ten sizes of sleeves 105 are required in the kit having outsidediameters D₇ sized to slip within, in close tolerance, the ten sizes ofdrill tubes 92. The inside diameter D₁₀ is selected to be slightlygreater (e.g., 0.5 mm larger) than the minor outside diameter D_(m) ofthe implants 10.

L. STARTER VERTEBRAL REAMER

To start a bore between opposing vertebrae, a starter vertebral reamer112 is provided (FIGS. 15 through 18). The starter reamer 112 has ashaft 114. A reamer head 116 is secured to the distal end of the shaft114. An axial face of the reamer 116 has a threaded bore 118 sized toreceive the threaded shaft 70 of the vertebral reamer guide pin 64. Aproximal end 120 has an outwardly flared hub 122 to act as a positivestop against flare 110 of the drill tube sleeve 106 as will be morefully described. A shaft 124 extends from the distal end. The reamer 116includes cutting blades 117 that provide both end cutting and sidecutting into bone as the starter reamer 112 is rotated about its axis.

To accommodate ten sizes of implants, ten sizes of vertebral reamers 112are included in the kit. The reamers 112 have outside diameters D₁₁equal to the minor outside diameters D_(m) of the implants 10.

M. FINAL VERTEBRAL REAMER

A final vertebral reamer 126 (FIGS. 34 through 37), is provided forcompleting a bore started by the starter vertebral reamer 112. The finalreamer 126 includes a shaft 128. A distal end of the shaft is providedwith a reamer end 130 having side and end cutting blades 131. A proximalend of the shaft is provided with an outwardly flared hub 132. Extendingfrom hub 132 is an axial shaft 134. For reasons given with respect tostarter reamer 112, ten sizes of final reamers 126 are required with thekit. The outside diameter D₁₂ of final reamer 126 equals the minoroutside diameter D_(m) of implants 10.

N. VERTEBRAL REAMER HAND DRIVER

To operate reamers 112 and 126, a hand driver 136 (FIGS. 46 and 47) isprovided. The hand driver includes an axial bore 138 to receive eitherof shafts 124 or 134. The hand driver 136 also includes a manuallyengageable handle 140 to be actuated by a surgeon performing the surgeryof the present invention.

The handle has an enlarged barrel portion 137 with radial grooves 139.With one hand, a surgeon puts axial pressure on handle 140 and with theother hand the surgeon rotates barrel 137 with fingers in grooves 139.Thus, the surgeon can securely turn a reamer secured to the driver 136.

Radial bores 141,143 extend through barrel 137 to receive set screws tofix a shaft 124 or 134 received within bore 138.

O. BONE TAP

In the event a threaded implant is utilized (as is the case in thepreferred embodiment of the present invention), the bores for theimplant are partially prethreaded. To prethread, a bone tap 142 (FIGS.40 through 42) is provided, having a shaft 144. At the distal end of theshaft 144 is a tapping head 146 having tapping threads 148. Near theproximal end of the shaft 144 is an enlarged diameter portion 156 havingan outwardly flared flange 158. A handle 160 is secured to the enlargedportion 156. The shaft 144 is also enlarged at portion 162 adjacenttapping head 146. The enlarged portion 156 is sized with diameter D₈ tobe received, in close tolerance, within the drill tube 92 such that thetube 92 will guide the tap 142 as will be more fully described.

Since ten sizes of implants 10 are intended to be utilized, ten sizes ofbone taps 142 are required. Diameter D₈ is equal to the major outsidediameter D_(M) of implant 10. The head 146 has a minor outside diameter(i.e., the diameter without threads 148) equal to the minor outsidediameter D_(m) of the implants 10.

P. IMPLANT DRIVER

To place implant 10, an implant driver 164 (FIGS. 43 through 45) isprovided. The driver 164 includes a shaft 166 having a reduced diameterdistal portion 166a. A distal end of the shaft 166 is provided with ahub 168 sized to be received within slot 24 of the implant 10 to urgethe implant 10 to rotate as the implant driver 164 is rotated. Theimplant driver 164 includes a stepped enlarged portion 170 including afirst diameter portion 172, a second diameter portion 174 and a thirddiameter portion 176 to accommodate the different diameters of drilltubes 92. A handle 178 is secured to the shaft 164. Grooves 180, 180aare formed on the shafts 166, 166a and extend along their axial lengths.The grooves 180 provide a means for a surgeon to sight the alignment ofthe implant.

FIGS. 45A and 45B show the implant driver 164 with a collet 171. Thecollet 171 has a cylindrical, knurled body 173 slidably carried on shaft166a. A pin 175 extending from body 173 into groove 180a permits collet171 to slide on shaft 166 but not rotate. Four prongs 177 extend axiallyfrom body 173 toward hub 168.

In use, shaft 166 is passed through end opening 24 of implant 10. Hub168 is receiving within slot 25. The prongs 177 are forced by a surgeonpushing on body 171 for the prongs 177 to be urged between opposingsurfaces of the implant 10 and shaft 166a to thereby securely capturethe implant 10 on driver 164. As a result, the implant 10 cannotinadvertently fall off. (For ease of illustration, the Figures showingthe method of the invention, FIGS. 48-63A, do not show use of collet171).

Q. ENDCAP INSERTER

Once an implant is placed between two vertebrae an endcap must besecured to the implant according to the preferred embodiment. To thisend, an endcap inserter 180 (FIGS. 19 and 20) is provided. The inserter180 includes a shaft 182. At the distal end of the shaft, a head 184 isprovided having a cupped surface 186 to receive and temporarily hold anendcap 26 before it is secured in place. An enlarged portion 180 of theshaft is sized to be received, in close tolerance, within drill tube 92to be guided by the tube 92. Since ten sizes of drill tubes are requiredfor ten sizes of implants, ten sizes of endcap inserters are alsorequired. The inserter 180 has an outside diameter D₁₄ just smaller than(e.g., 0.5 mm smaller) than the inside diameter D₆ of the drill tube 92.A knurled handle 190 is provided on the proximal end of the shaft 182.

R. SLAP HAMMER

To remove the distraction plug 54 of drill tube guide 72, a slap hammer192 (FIGS. 26 and 27) is provided. The slap hammer is a cylindrical bodyhaving a knurled surface to permit a surgeon to securely grip the body.The hammer has an axial slot 196. The hammer is placed on the shafts202, 50 of handle 200 or inserter 48, respectively, with the tool shaftreceived within slot 196. By pulling back on hammer 192 and impacting itagainst a stop surface (e.g., surface 49 of tool 48), a tool can beremoved.

S. DRILL TUBE GUIDE REMOVAL HANDLE

A handle 200 (FIG. 11) is provided to remove the drill tube guide 72.The handle 200 includes a shaft 202. At the distal end, a threaded stub204 is provided sized to be threadably received within the threaded bore81 of the drill tube guide 72. A proximal end of the handle 200 isprovided with an enlarged diameter knurled handle 206 to permit asurgeon to securely grasp the handle 200 and to stop the travel of slaphammer 192.

T. DRILL TUBE SHEATH

As will become apparent, drill tube 92 or planar 84 are passed through apatient's body to an implant site. To avoid risk of teeth 85 or 98damaging vessels, nerves or organs, a drill tube sheath 300 is provided(FIGS. 29A, 29B). The sheath 300 is a hollow tube with inside diameterD₁₅ slightly smaller than the outside diameter of drill tubes 92 orplanars 84 (accordingly ten sizes of sheath 300 are required). Thesheath 300 has an axial slit 301 extending its entire length. The sheath300 has a blunt distal end 302 and a flared proximal end 304.

The sheath is slipped onto the drill tube 92 or planar 84 with end 302extending beyond the teeth 85 or 98 (see FIG. 64A illustrating use ofsheath 300 with drill tube 92). As the planar 84 or drill tube 92 arepassed to an implant site the blunt end 302 covers the teeth andprevents the unwanted cutting of vessels, nerves or organs. When pressedagainst vertebrae, the end 302 abuts the vertebrae. With continuedadvancement of the tube 92 or planar 84 toward the vertebrae, the sheath300 slides on the planar 84 or tube 92 until teeth 85,98 abut thevertebrae.

In the method of the invention, sheath 300 remains in place wheneverplanar 84 or drill tube 92 are used. However, for ease of illustration,sheath 300 is not shown in FIGS. 46-63A.

3. POSTERIOR TECHNIQUE

A. Surgical Approach

The present invention will first be described with reference to use in aposterior approach. In a posterior approach, a surgeon seeks access tothe spine through the back of the patient. An alternative approach is ananterior approach where the surgeon seeks access to the spine throughthe abdomen of a patient. The anterior approach can be done through opensurgery or through laparoscopic surgery.

While a posterior approach will be described in detail, it will beappreciated that the present invention can be used in an anteriorapproach for both laparoscopic or non-laparoscopic procedures.

Once a surgeon has identified two vertebrae which are to be fusedtogether, the surgeon identifies an implant of desired size and thesurgeon determines the desired amount of distraction to be requiredbetween the vertebrae before placement of the implant. In selecting theimplant size, the surgeon should ensure that the device will remainwithin the lateral borders of the intervertebral disc while alsopenetrating at least 3 mm into the vertebral bodies cephalad and caudalto the disc.

In the posterior technique, a patient is placed on the operating tablein either a prone or kneeling-sitting position. At the discretion of thesurgeon, the spine is flexed slightly. Anesthesia is administered.

Exposure of the intervertebral disc is obtained through any suitabletechnique well-known in the art. The facet of the vertebrae is removedin as limited amount as possible to permit insertion of the instrumentsand the implants. Preferably, bone dissected from the lamina, facets andspinous process are preserved for later use as bone graft.

Referring to FIG. 48, two vertebrae 210, 212 are separated by a disc214. The disc 214 is shown in plan view in FIG. 48A. As shown in thefigures, no procedure has yet been performed on the disc such that thedisc 214 is in a relaxed, undistracted state.

B. Identifying Desired Implant Locations

After having selected the implant size, the surgeon selects the starteralignment guide assembly 36 and secures the handle 28 to the assembly 36by threading shaft 32 into bore 42. The prongs 44, 46 of the guide 36are placed on either side of the cauda equina such that they are atmid-disc height and equidistant from the mid-sagittal plane. The guideis pressed ventrally to make two points 44a, 46a on the disc for implantinsertion as shown in FIGS. 49, 49A. The two points 44a, 46a mark rightand left side desired implant location points. For the purposes of thisdiscussion, right and left will mean with respect to the view of theback of the spine as viewed by the surgeon performing the surgerythrough the posterior approach.

After the starter alignment guide 36 is urged into position as shown inFIGS. 49, 49A, the handle 28 is unscrewed and removed from the guide 36.Lateral and anterior-posterior x-rays or C-arm fluoroscopy are taken ofthe alignment guide 36 to verify its orientation within the disc space.If the alignment guide 36 is determined to be correctly positioned, itis removed from the disc space by reattaching handle 28 and pulling theguide 36 out. A limited discectomy is performed through the two openings44a, 46a in the disc to permit insertion of a distraction plug 54.

C. Left Side Distraction

Once the left and right side desired implant locations are identified byplacement of the starter alignment guide 36, and after the guide 36 isremoved, the surgeon selects a side (i.e., left or right) in which toinitiate the distraction procedure. Beginning with the left side forpurposes of example, the distraction plug inserter 48 is secured to adistraction plug 54 by threading end 52 into bore 62. The distractionplug 54 is forced into the disc space at the indent 46a made at the leftside of the vertebrae by the prong 46 (see FIGS. 50 and 50A). The sizeof distraction plug 54 is selected to distract the annulus fibrosuswithout causing damage to the surrounding vertebral bone, annular fibersor spinal nerves. Accordingly, it is recommended the surgeon initiallyinsert a relatively small plug 54 (for example, 8 mm) followed bysuccessively larger plugs until the annulus is distracted to thesurgeon's satisfaction. Once the correct maximum size distraction plug54 has been chosen, it is left in place and the handle 48 removed asshown in FIGS. 51 and 51A. The disc 214 has now been stretched so that aparallel distraction of the opposing end plates 210′,212′ of thevertebrae 210,212 has occurred on both the left and right sides. Thedistraction plug 54 is fully inserted such that it is either flush orslightly recessed within the disc space.

In performing the procedures of the present method, the surgeon takescare to retract the cauda equina and nerve roots from the area beingprepared for the drill 92 as will be described. To this end, thedistraction plug 54 is placed recessed. As a result, the cauda can bemoved over into the region of the distractor plug 54 without thedistractor plug 54 damaging the cauda equina.

D. Right Side Alignment

Once the distraction plug 54 is inserted as shown in FIGS. 51, 51A, thesurgeon proceeds to the right side location 44a. The vertebral reamerguide pin 64 is secured to the drill tube guide 72 by threading theshaft 70 within the bore 80. The guide pin 64 selected is preferably thesame diameter as the final distraction plug 54 left in place within thedisc space on the left side. As a result, upon insertion of the guidepin 64 as shown in FIGS. 52, 52A, the guide pin 64 abuts the opposingend plates 210′,212′ of the vertebrae 210,212 as does plug 54. The axisof pin 64 is equidistant from the end plates 210′,212′.

E. Planing Vertebral Surface

The surface of the vertebrae 210, 212 against which tools are to beplaced should be smooth with the surface of the two vertebrae 210, 212aligned. Frequently, this condition will not naturally exist. Therefore,the vertebrae 210, 212 must be pre-planed to a flat surface.

If planing is deemed necessary by the surgeon, the drill tube planar 84is passed over the drill tube guide 72 with the rasp end 88 abutting thedisc material 214 and vertebrae 210, 212 or tissue (not shown) on thevertebrae as shown in FIG. 53, 53A. The interior diameter of the planar84 is selected to have a close tolerance with the exterior diameter ofthe drill tube guide 72. As a result, the planar 84 can rotate on thedrill tube guide 72 and move axially relative thereto but cannot movelaterally relative to the tube guide 72. The surgeon rotates the planar84 to rasp a planed flat surface on the vertebrae. The rasping willprovide a smooth surface for placing of the drill tube as will bedescribed. For purposes of illustration, the rasp end 88 is shown deeplyreceived with the vertebrae after rasping.

The drill tube guide 72 prevents planar 84 from excessive axiallymovement. Namely, when planar 84 is fully advanced, surface 87 abutssurface 83 signalling completion of the rasping operation.

F. Fixing Right Side Alignment

After the surface of the vertebrae has been planed smooth, the planar 84is removed and the appropriately sized drill tube 92 is passed over thedrill tube guide 72 (see FIGS. 54, 54A). The teeth 98 of the drill tube92 are secured to the posterior vertebral bodies using the drill tubeinserter cap 100 to pound the teeth 98 into the vertebral bodies 210,212. The drill tube guide 72 and the vertebral reamer guide plug 64 arethen removed from the drill tube 92 leaving the drill tube 92 in placeand with the teeth 98 thereby retaining the vertebral bodies in thedistracted state. To remove the guide 72, handle 18 is attached to guide72 by threading stud 204 into bore 84. The surgeon uses the slap hammer192 to remove the guide and handle assembly.

FIG. 64 illustrates use of the cap 100 to advance teeth 98 into thevertebrae 210,212. As shown, the drill tube guide 72 is longer thandrill tube 92. With teeth 98 aligned with end 78, end 83 protrudesbeyond flange 99. The cap 100 is positioned as shown in FIG. 22A. Thecap is sized for the distance, X, between surfaces 83,103 to be about 3mm when teeth 98 are flush with end 78. Pounding on surface 104, teeth98 are driven in 3 mm until surface 103 stops against surface 83. Theflats 97 of the teeth 98 prevent further advancement of the drill tube92 into the bone.

The drill tube 92 has an inside diameter approximate to the outsidediameter of the drill tube guide 72. Accordingly, the drill tube guide72 accurately places the drill tube 92 in proper alignment. In thisalignment, the tube 92 has its axis equidistant from the end plates210′,212′ of vertebrae 210, 212. Since all insertion tools and tubes ofthe kit have lengths sized off of the drill tube guide 72, the guide 72′insures that a final desired depth of implant penetration is attained.

G. Placement of Drill Tube Sleeve

With the drill tube guide 72 and the vertebral reamer guide plug 64removed from the drill tube 92, a drill tube sleeve 106 is placed in thedrill tube with the top end 110 abutting the topend 99 of the drill tube92. As shown in FIGS. 55, 55A, when the sleeve is fully inserted, itsflared end 110 abuts the flared end of the drill tube.

H. Pre-Boring of Implant Bore

The vertebral reamer guide pin 64 is then threaded on to the startervertebral reamer 112. The guide pin 64 used is the same pin 64previously used on the drill tube guide 72. The cavity 65 (FIG. 55) leftafter removal of the pin 64 (described in step G, above) receives thepin 64/reamer 112 assembly to guide the reamer 112 such that the reamer112 cuts equal amounts of bone from both vertebrae 210,212.

The starter vertebral reamer 112 is inserted into the drill tube sleeve106 and then a bore is partially reamed until a shoulder 122 on thereamer 112 abuts the drill tube sleeve 106 as shown in FIGS. 56, 56A.The hand driver 136 (FIG. 46) is used to turn reamer 112. However, forease of illustration, the driver 136 is not shown in FIGS. 56, 56A. Thereamer 112 and the drill tube sleeve 106 are then removed from the drilltube 92 (see FIGS. 57, 57A) exposing a pre-drilled bore 200 with adiameter equal to the minor outside diameter D_(m) of implant 10.

I. Final Reaming

The preparation of the implant bore is then completed by inserting thefinal vertebral reamer 126 into the drill tube 92 (FIGS. 58, 58A). Thereamer 126 is rotated with driver 136 (not shown in FIG. 46) until theshoulder 132 on the reamer 126 meets the flared end of the drill tube 92to thereby provide a positive stop.

Since bore 200 is pre-drilled, a drill sleeve 106 is not required forfinal drilling since the bore 200 initially guides final reamer 126.This provides greater clearance and ease of operation of final reamer126. The final reamer 126 is removed leaving a fully drilled implantreceiving bore 220 with a diameter equal to the minor outside diameterD_(m) of implant 10 (see FIGS. 59 and 59A).

In the foregoing, the reader will note that the lengths of the variousdrill tubes, drill tube sleeves and reamers are selected such that theflared ends provide accurate depth of reaming between the vertebralbodies. Also, the reader will note that both vertebrae 210, 212 areequally drilled. Additionally, the reader will note the pre-boring ofstep H, above, ensures the final bore 220 is cut parallel to end plates210′,212′ and equally cut into both vertebrae 210,212.

J. Bone Tap

In the event a threaded implant is used (as is the case in the preferredembodiment), a bone tap 142 is passed through the drill tube 92 androtated to partially pre-tap the bore 210. The tap is introduced untilthe stop 158 on the handle abuts the top of the drill tube 92 as shownin FIGS. 60, 60A.

The tap is then removed to expose a partially tapped, fully boredimplant bore 300 with the drill tube 92 remaining in place (see FIGS. 61and 61A).

K. Placing Implant

The front chamber 16 of the implant 10 is packed with bone graft. Thegraft may be autograft obtained previously from the iliac crest or someother graft material (e.g., allograft or artificial bone). The implant10 is attached to the implant driver 164 by placing the hub 188 withinthe slot 24 and securing the implant with collet 171 (not shown in FIGS.62, 62A). The implant 10 is then passed into the drill tube 92 (FIGS.62, 62A). The implant 10 is threaded into the bore 300 with implantdriver 168 by the surgeon rotating the driver 168 and advancing it intothe tube 92 until the driver stop 176 contacts the top of the drill tube92.

It is desirable that the large holes 21 of the implant are oriented in asuperior-inferior direction (i.e., the large holes are facing thevertebrae). This orientation is guaranteed by orienting the slots 180 inthe implant driver 168 to be vertical.

After the implant 10 is fully in place (recessed into bore 300), theimplant driver 168 and the drill tube 92 are removed from the right-sidehole (see FIGS. 63 and 63A). Simply pulling on driver 164 releases theimplant 10 from the collet 171.

At this point in the procedure, it is recommended that the surgeonobtain a lateral radiograph or C-arm fluoroscopy to verify thepositioning of the implant 10 within the intervertebral space. If properpositioning has been obtained, the back chamber 17 of the implant 10 ispacked with bone graft. Alternative to the above, the drill tube 92 maybe left in place with the graft inserted to chamber 17 through tube 92.If removed, tube 92 is repositioned after chamber 17 is filled. Thepolyethylene endcap 26 is attached to the end of the implant 10 with theendcap inserter 180 by passing the endcap through the drill tube 92.

At this stage in the procedure, the right side implant is fullyinserted.

The reader will note in placing the implant 10, the movement of driver164 is limited by stop 176. If a smaller implant 10 is used (and hence asmaller diameter drill tube 92), the movement is stopped by surface 174or 176 (see FIG. 43).

L. Left Implant and Closure

The surgeon returns to the left side and removes the distraction plug 54by threading the handle 48 into the distraction plug 54 and pulling itout using slap hammer 192. If, for any reason, the threaded stud 52 onhandle 48 were to break, the reduced diameter portion 55 of plug 54permits a surgeon to pull on flange 57 to remove plug 54.

The left side is now prepared for receiving an implant in a manneridentical to that described above for the right disc space with theprocedures identified in FIGS. 52 through 63A.

After the right and left implant are fully inserted, it is recommendedthat a lateral radiograph be taken of the implants. Assuming properpositioning, bone graft is impacted between and surrounding the implantsto better facilitate fusion. The wound is closed.

4. OTHER SURGICAL PROCEDURES

The foregoing procedure illustrates the method of the present inventionwith respect to a posterior approach. However, the identical procedurecan be used with an anterior approach. Also, those skilled in the artwill note that the present procedure is readily adaptable to alaparoscopic approach. Through placement of a cannula (not shown) in alaparoscopic approach, all the procedures can be performed through thecannula with the various tubes and sleeves described above passedthrough the cannula and accurately placed.

All of the foregoing tools of the kit of the invention can be passedthrough a cannula except for alignment guide assembly 36. Instead ofusing assembly 36 in a laparoscopic approach, the implant sites can bemarked through any other suitable technique or a collapsible alignmentguide assembly can be provided to pass through a cannula.

In addition to the above, the method and tools of the invention can beused with a single implant (either a threaded implant 10, a non-threadedimplant or a bone or any other implant). In this method, the plug 54 isinserted at a desired site. The plug 54 is then removed and the pin 64inserted into the same site using the guide 72. All procedures describedabove are then used to form an implant receiving bore.

From the foregoing detailed description of the present invention, it hasbeen shown how the objects of the invention have been obtained in thepreferred manner. However, modifications and equivalents of thedisclosed concepts such as those which would occur to one of ordinaryskill in the art, are intended to be included within the scope of thepresent invention.

1. A surgical method for implanting at least two spinal fusion implantsinto a disc space of disc material separating a first and secondvertebrae, said disc space and first and second vertebrae divisible intofirst and second sides separated by a sagittal plane, said methodcomprising the steps of: (a) inserting a first rigid distraction spacerinto said a non-distracted disc space at a desired first implantlocation on said first side with said first distraction spacer sized forexternal surfaces of said first distraction spacer to act against firstand second end plates of said first and second vertebrae, respectively,to urge said first and second vertebrae apart upon said insertion,thereby distracting said first and second vertebrae, said spacer fullyinserted for said spacer so as to be completely recessed within saiddisc space so as not to substantially protrude beyond said space withinthe perimeter of said first and second end plates; (b) placing a guideat said second side while maintaining distraction at said first implantlocation with said distraction spacer and with said guide adapted todirect tools axially through an axis parallel to and equidistant betweenopposing end plates of said first and second vertebrae; (c) forming asecond implant bore at a desired second implant location by removingbone material from said first and second vertebrae and by removing discmaterial at said second implant location with said second implant boresized to receive said second implant, said forming of said second boreutilizing at least a first boring tool guided by said guide; (d)implanting said second implant into said second implant bore; (e)removing said first distraction spacer and applying a guide to saidfirst side; (f) forming a first implant bore at said desired firstlocation by removing bone material from said first and second vertebraeand by removing disc material at said first implant location with saidfirst bore sized to receive said first implant, said forming of saidfirst bore utilizing at least a first boring tool guided by said guideat said first side; and (g) implanting said first implant into saidfirst implant bore.
 2. A method according to claim 1 wherein said stepof placing a guide at said second side includes: (a) providing a guidetube having an open first end and an open second end with attachmentmeans on said first end for securing said first end to said first andsecond vertebrae; and (b) placing said first end against said first andsecond vertebrae with said guide tube aligned with said second implantlocation.
 3. A method according to claim 2 wherein said step of formingsaid second bore includes inserting a boring tool into said guide tubewith said boring tool sized to form said second implant bore andoperating said boring tool to bore into and remove said bone materialwhile guiding said boring tool with said guide tube.
 4. A methodaccording to claim 2 wherein said implant is inserted through said guidetube.
 5. A method wherein according to claim 1 wherein said step ofapplying said guide to said first side includes: (a) providing a guidetube having an open first end and an open second end with attachmentmeans on said first end for securing said first end to said first andsecond vertebrae; and (b) urging said first end against said first andsecond vertebrae with said guide tube aligned with said first implantlocation.
 6. A method according to claim 1 wherein said step of placingsaid guide at said second side includes comprises: inserting a guide pininto said disc space at said second implant location with the guide pinselected to be of a size approximate to a size of said distractionspacer; providing a guide tube having an open first end and an opensecond end with attachment means on said first end for securing saidfirst end to said first and second vertebrae; and urging said first endagainst said first and second vertebrae with said tube aligned by saidguide pin to be in alignment with said second implant location.
 7. Amethod according to claim 6 wherein said step of forming said secondimplant bore includes removing said guide pin through said guide tubeafter said urging of said first end against said first and secondvertebrae and inserting a boring tool into said guide tube with saidboring tool sized to form said second implant bore and operating saidboring tool to bore into and remove said bone material while guidingsaid boring tool with said guide tube.
 8. A method according to claim 6wherein a guide pin of a size substantially equal to said guide pin usedto align said guide tube is secured to a boring tool to prebore saidsecond implant bore with said tool and attached guide pin inserted intosaid guide tube and operated to partially bore into said vertebrae to adesired depth.
 9. A method according to claim 6 comprising providing atube guide attached to said guide pin and passing said guide tube oversaid tube guide to place said tube against said vertebrae in a desiredposition with said tube guide aligning said guide tube.
 10. A methodaccording to claim 8 wherein said desired depth is less than a finisheddepth, removing said boring tool and attached guide pin through saidguide tube and inserting a finish boring tool into said guide tube andoperating said finish boring tool to finally bore form a finished borebetween said vertebrae.
 11. A method according to claim 1 wherein saiddistraction spacer is inserted into said desired first implant locationto a depth sufficient to move a patient's anatomical features towardsaid first implant location without interference from said distractionspacer.
 12. A surgical method for implanting at least two spinal fusionimplants into a disc space of disc material separating a first andsecond vertebrae, said disc space and first and second vertebraedivisible into first and second sides divided by a sagittal plane; saidmethod comprising the steps of: (a) placing a distraction spacer betweensaid undistracted vertebrae, said spacer fully inserted so as to becompletely recessed within said disc space within the perimeter of firstand second end plates of said first and second vertebrae, respectively,at one of said sides first side with said distraction spacer having afixed size for external surfaces of said distraction spacer actingagainst said first and second end plates of said first and secondvertebrae, respectively, to distract said vertebrae as said distractionspacer is inserted into said disc space; (b) forming a first implantreceiving bore in the other of said sides second side while retainingsaid distraction plug spacer in place at said one of said sides firstside, said forming including using a guide pin having external surfacesspaced apart substantially equal to a spacing of said external surfacesof said distraction spacer to place a guide at said other of said sidessecond side to guide a boring tool along an axis parallel to and equallyspaced from end plates of said vertebrae, said forming further includinginserting said guide pin into said disc space with said externalsurfaces of said guide pin guided by said end plates for said guide pinto be centrally positioned between said vertebrae and with an axis ofsaid guide pin substantially parallel to said end plates; and (c)inserting a first implant into said first bore and removing saiddistraction spacer and forming a second finished bore in said first sidesized to receive a second implant and placing said second implant insaid second bore.
 13. A method according to claim 12 comprisinginserting a first implant into said first bore and removing saiddistraction spacer and forming a second finished bore in said one ofsaid sides sized to receive a second implant and placing said secondimplant in said second bore.
 14. A method according to claim 13 12wherein said bores are formed on a posterior side of said vertebrae. 15.A method according to claim 13 12 wherein said bores are formed on ananterior side of said vertebrae.
 16. A method according to claim 13 12wherein said bores are formed laparoscopically.
 17. A method accordingto claim 12 wherein said distraction spacer is placed between saidvertebrae to a depth sufficient to move a patient's anatomical featurestoward a location of insertion of said distraction spacer withoutinterference from distraction spacer.
 18. A method for implanting aspinal fusion implant into a disc space of disc material separatingopposing end plates of a first and second vertebrae, said methodcomprising the steps of: (a) securing a guide pin to a drill tube guideof predetermined dimensions with said guide pin sized approximate to adesired distraction of said vertebrae and inserting said guide pin intosaid disc space with external surfaces of said guide pin guided by saidend plates for said guide pin to be centrally positioned between saidvertebrae and with an axis of said guide pin substantially parallel tosaid end plates; (b) placing a guide tube over said drill tube guide andsecuring said guide tube to said first and second vertebrae; (c)removing said guide pin and said drill tube guide through said guidetube while retaining said guide tube secured to said first and secondvertebrae; (d) attaching said guide pin to a first boring tool formovement therewith; (e) boring an implant bore between said first andsecond vertebrae by inserting athe first boring tool and attached guidepin into said guide tube, said boring including providing a boring toolwith a guide pin, sized substantially equally to said guide pin securedto said drill tube guide, secured to said boring tool for movementtherewith and at least partially boring said implant bore to a firstdepth, said first depth being less than that required for fullyimplanting the implant, with said guide pin guiding said boring toolbetween said vertebrae; and (f) removing said boring tool and attachedguide pin and inserting a second boring tool to bore said bore to asecond depth.
 19. A surgical method for implanting a spinal fusionimplant into a disc space of disc material separating opposing endplates of a first and a second vertebrae, said method comprising thesteps of: at least partially forming a bore for receiving said implantby inserting a boring tool into said disc space and rotating said boringtool to at least partially bore into each of said first and secondvertebrae, said forming including providing attaching a guide on pin toa distal end of said boring tool with said guide pin having a cuttingtip for removing disc material and a guide body, said guide bodyincluding diametrically opposite external surfaces spaced apart adistance equal to a desired distraction of said vertebrae, said guidepin secured to said boring tool for movement therewith, said formingfurther including inserting said guide pin between said end plates withsaid end plates guiding said external surfaces to retain said guide pincentrally positioned between said end plates and with an axis of saidguide pin generally parallel to said end plates, said forming stillfurther including advancing said boring tool into said disc spacingspace to a first depth, said first depth being less than that requiredfor fully implanting the implant, with said guide pin maintaining anaxis of said boring tool generally coaxial with- said axis of said guidepin.
 20. A surgical method for implanting a spinal fusion implant into adisc space for of disc material separating opposing end plates of afirst and second vertebrae, said method comprising the steps of:providing a guide tool having external dimensions sized to be receivedwithin a guide tube and having a guide pin on a distal end of said guidetool with said guide pin having at least one cutting surface forremoving disc material, the guide pin having external surfaces spacedapart approximate to said a desired distraction; inserting said guidepin into said disc space with said end plates guiding said externalsurfaces for said end plates to retain an axis of said guide pin andsaid guide tool generally parallel to and centrally received betweensaid vertebrae and with said vertebrae distracted at least afterinsertion of said tool; providing said guide tube with teeth on a distalend thereof and placing said guide tube over said guide tool with saidteeth opposing said vertebrae and with said guide tool maintaining anaxis of said guide tube generally parallel to and centrally receivedbetween said vertebrae; urging said guide tube distal end against saidvertebrae for said teeth to penetrate into said vertebrae; placing aprotective sleeve over an exterior of said guide tube before urging saidguide tube distal end against said vertebrae with said sleeve sized tomove slidably on said guide tube in a direction generally parallel tosaid axis of said guide tube and with said sleeve having a blunt distalend extending beyond and cover covering said teeth; said urgingincluding said blunt distal end against said vertebrae and urging saidteeth into said vertebrae whereby said blunt distal end covers saidteeth and abuts said vertebrae until said teeth penetrate into saidvertebrae; and removing said guide pin and said guide tool through saidguide tube.
 21. A method according to claim 19 wherein attaching saidguide pin includes attaching said guide pin having a cylindrical bodythat defines a reduced diameter as compared to the boring tool.
 22. Amethod according to claim 19 wherein attaching said guide pin includesattaching said guide pin having attachment structure for detachablysecuring said guide pin to said distal end of said boring tool, andfurther including securing said guide pin to said distal end of saidboring tool.
 23. A method according to 22 wherein said attachmentstructure includes a threaded connection, and securing said guide pinincludes threading said guide pin to said distal end of said boringtool.